Irradiation of wax



United States Patent IRRADIATION F WAX Herman L. Thwaites, Clark, andJames F. Black, Roselle,

N.J., assignors to Esso Research and Engineering Company, a corporation'of Delaware No Drawing. Application January 27, 1956 Serial No. 561,948I 3 Claims. (Cl. 204-154) This invention relates to wax and moreparticularly relates to the irradiation of petroleum waxes and to theirradiated wax products. Still more particularly, the present inventionrelates to the process of subjecting crystalline petroleum waxes to highintensity ionizing radiation from an atomic pile whereby the normalparafiin content of the wax is charged.

Waxes such as those obtained from'petroleum are employed extensively ascoatings for paper and paper cartons. The particular end uses of thesewaxes dictate the desired properties or characteristics of the waxes.For example, waxes which are employed in coating paper (e.g., to makebread wrappers and the like) should be relatively hard and have a highnormal paralfin content. On the other hand, waxes which are employed forcoating paper cartons (e.g., milk and food cartons) should be relativelyflexible and have a lower normal paraffin content and a higherisoparaflin content. Although the normal paraflin content of petroleumwaxes can be varied to a certain extent by refining methods, frequentlyit is necessary to employ different crude oils as sources for differenttypes of waxes. The necessity, therefore, of segregating and processingtwo or more different types of crude oil specifically for waxmanufacture complicates petroleum processing, particularly in a smallrefinery. It would, therefore, be highly desirable to develop a simple,inexpensive and effective method for modifying the properties, and moreparticularly the normal paraffin content, of waxes derived from a givencrude oil.

In accordance with the present invention, a novel method has now beenfound for modifying the properties of agive'n wax and more particularlyfor changing the normal paraffin content of such wax. This method of thepresent invention comprises subjecting the wax to high intensityionizing radiation whereby thenormal paraffin content of the wax ischanged. The present invention is most eliectively carried out whensubjecting petroleum wax to the radiation from an atomic pile. It hasbeen found that relatively low radiation dosages will increase thenormal paraffin content of the wax, whereas relatively high radiationdosages will decrease the normal parafiin content of the wax. Thus bymeans of the present invention it is possible to simply and effectivelymodify theproperties of the Wax by irradiation to make, if desired,either a hard wax useful as a paper coafingor to make a more flexiblewax useful for coating paper cartons. In accordance with the preferredmethod of' the present invention, the wax is irradiated prior to its:conventional finishing steps such as the final! deoiling step and/orfinal distillation step.

The present method is particularly applicable to petroleum waxes,:especially to crystalline waxes melting Within the range of about 100 to165 F., e.g., 120

2,904,482 Patented Sept. 15, 1959 to 150 F. The waxes which may beirradiated in ac cordance with the present invention may be (1) refinedwaxes having oil contents below about 0.5% by Weight, (2) crude scalewaxes having oil contents in the range of about 0.5 to 5% by weight or(3) relatively high oil content waxes, such as slack waxes from plateand frame presses or petrolatum from solvent deWaXing plants, having oilcontents in the range of about 5 to 50% by weight. These petroleum waxesmay be ob tained from a variety of crude oils such as, for example, EastTexas, Panhandle, Louisiana, San Joaquin, Mid-Continent, Pennsylvania,etc. Generally the crystalline paraffin waxes will contain 1) about to97% by weight of normal (straight chain) paraflins, (2) about 3 to 16%by weight of iso (branched chain) paraflins and (3) about 0 to 15% byweight of naphthe'nes (saturated cyclic rings.

The above-described waxes are subjected to high intensity ionizingradiation and more particularly to high intensity radiation comprisingneutrons and gamma rays. In the preferred embodiment of the invention,the waxes are subjected to the radiation from an atomic pile (or nuclearreactor) which consists essentially of gamma rays and neutrons.Generally the gamma ray fluxes from atomic piles will be about 10 to6x10 usually about 10 to 3 1O roentgens per hour. The neutrons in thepile are of two general types, namely, slow (thermal) neutrons and fastneutrons. Slow neutrons are generally considered to be those neutronshaving an energy of less than about 100 electron volts. The presentprocess is most effectively carried out employing fast neutrons, thatis, neutrons having an energy more than about 100 electron volts.Generally these fast neutrons will have an energy in the range of about100 to 2x10 usually an energy in the range of about 3 10 to 1 10electron volts. The fast neutron flux will generally be in the range ofabout 10 to 10 usually about 10 to 10 neutrons/cm. /sec. The slow(thermal) neutron flux existing in the atomic piles generally will be inthe range of about 10 to 10 usually about 10 to 10 neutrons/cm. /sec.Beta rays are also produced in an atomic pile. However, as beta rayshave low penetration, they are absorbed principally in the metals whichclad the fissionable fuel elements. Therefore, these rays are relativelyinsignificant as compared to the gamma rays and neutrons.

The irradiation may be carried out on either a batch or continuousbasis. More specifically, for example, a batch operation can be carriedout simply by exposing the wax in a container to the high intensityionizing radiation. To carry out a continuous process, the wax in liquidform may be pumped through pipes disposed in the atomic pile. The waxmay be irradiated at a temperature of about 0 to 400 F., preferablyabout 60 to 300 F. It will usually be most convenient to carry out theirradiation at about atmospheric pressure although it will be understoodthat higher (e.g., l to 10 atmospheres) or lower pressures may beemployed if desired. The irradiation may be carried out in the presenceor absence of air or may be carried out in an inert atmosphere such asnitrogen.

The present process has a number of advantages over conventionalprocesses. More particularly, these advantages include: 1) The presentprocess may be conveniently carried out at atmospheric temperatures'andpressures. (2) The products of the present invention are free fromcontaminants such as catalyst residues and the like. In addition, thepresent process minimizes undesirable side reactions. (3) The presentprocess afiords a high degree of process control since controlledradiation dosages can be readily effected. (4) The present process isreadily adaptable to a continuous operation.

The time of irradiation will depend primarily upon the degree ofconversion desired as well as the radiation dosage rate available.Actual times may vary from a matter of a few seconds up to a week orlonger. As has been stated heretofore, relatively low radiation dosagesare employed to increase the normal parafiin content of the wax toproduce a harder wax. Generally, radiation dosages of about 0.001 to 3,preferably about 0.1 to 1 megaroentgens of gamma rays and about 3 x10 to10 preferably 3X10 to 3X10 fast neutrons/cm. will be employed for thispurpose. When employing such radiation dosages, the slow neutron dosagewill be about 3X10 to 10 usually about 3 10 to 10 slow neutrons/cmF. Onthe other hand, when it is desired to decrease the normal paraffincontent (and increase the isoparafiin content), the radiation dosageshould be about 3 to 500, preferably about 10 to 200 megaroentgens ofgamma rays and about 10 to 2x10 preferably 3 10 to 10 fastneutrons/cmfi. When using such radiation dosages, the slow neutrondosage will be about 10 to 2X10, usually about 3X10 to 10 slowneutrons/cmfi.

Upon completion of the irradiation in accordance with the presentinvention the irradiated wax product may be employed per se. However, ifdesired, the irradiated wax product may be further processed byconventional techniques. For example, the irradiated wax product may besubjected to distillation, preferably vacuum distillation, to cut aproduct of desired melting point or melting point range. Further, theirradiated wax product may be deoiled by conventional deoilingtechniques including sweating and solvent deoiling, which processes areWell known in the art. In the preferred embodiment of the presentinvention, the Wax is irradiated prior to one or more of its usualfinishing steps such as deoiling and/or distillation. In this way, anysmall amounts of undesirable side reaction products formed during theirradiation may be separated from the irradiated wax product. Forexample, when preparing a refined wax product to be used for coatingpaper or paper cartons, a crude scale wax (about 0.5 to weight percentoil) may be irradiated in accordance with the present invention and thendeoiled in a solvent (methyl ethyl ketone or propane) deoiling unit (orsweaters) to produce the refined wax product (less than about 0.5 weightpercent oil). As another example of this preferred modification of thepresent invention, a refined wax, which in the normal course of eventsis to be subjected to vacuum distillation, is irradiated in accordancewith the present invention prior to the final vacuum distillation step.Similarly, if desired, petrolatum or slack wax may be irradiated inaccordance with the present invention and then subsequently processedthrough the normal wax refining steps (such as solvent deoiling and/orsweating and/or vacuum distillation) to prepare a finished wax productsuch as crude scale wax or refined wax.

The invention will be more fully understood by reference to thefollowing example. It is pointed out, however, that the example is givenfor the purpose of illustration only and is not to be construed aslimiting the scope of the present invention in any way.

EXAMPLE A refined petroleum wax having a melting point of l32/134 F. wasirradiated in accordance with the pres ent invention. This refined waxcontained about 0.14 weight percent oil and was obtained from SanJoaquin crude by the following conventional processing steps, namely,distillation followed by solvent deoiling (methyl ethyl ketone-toluenemixture) for oil content reduction and sweating for melting pointseparation. This wax con- 4 tained about 92.5 weight percent normalparalfins, about 6.0 weight percent isoparaflins and about 1.5 weightpercent naphthenes.

Samples of this wax, which were contained in 10 cc. quartz ampules, weresubjected at about F. to irradiation from an atomic reactor. Theintensity of radiation at the time of these tests was about 0.69megaroentgen per hour gamma radiation, a slow neutron flux of 9 x10neutrons/cm. sec. and a fast neutron flux estimated at about 10 neutronsper cm. /sec. Samples of the wax after 1, 3, 8 and 168 hours ofirradiation were then evaluated, the results of which are summarizedbelow.

Pile irradiation of a fully refined parafifn wax It will be noted thatsignificant changes in the melting point and viscosity of the Wax wereachieved after as little as one hour of in-pile irradiation. The meltingpoint of the wax decreased generally during the irradiation periodwhereas the viscosity of the wax decreased during the first hour ofexposure and increased thereafter. This discontinuity in viscosity isdue to the destruction of small concentrations of radiation-sensitiveisoparaffins and to the resultant formation of normal paraffins duringapproximately the first hour of irradiation. Then after approximatelythe first hour under the present irradiation conditions, the normalparafiin content is decreased and the isoparaflin content is increased.A comparison of the viscosity and melting points shown in the abovetable with those values for pure compounds indicates that thesedesirable results are obtained.

The process of the present invention, as demonstrated above, isimportant since the proportions of isoparafiins present in a wax, eventhough small, have a marked influence on the end use characteristics ofwaxes. By means of the present invention, the branched parafiin waxcontent of a petroleum wax or wax feedstock may either be reduced orincreased depending upon the quantity of radiation employed. Such amethod can thus provide greater flexibility in the types of Waxes thatcan be produced and in the feedstocks which can be used as a source forproducing refined waxes.

In a corresponding experiment, the above-identified 132/ 134 F. refinedwax was subjected solely to gamma radiation. A radiation dosage of about5.5 megaroentgens of gamma radiation was found to have no measurableeflect on either melting point or viscosity.

What is claimed is:

1. A process for treating refined petroleum wax which comprisessubjecting said wax to ionizing radiation comprising fast neutrons ofintensity of at least about 10 neutrons per cm. per second and gammarays of intensity of at least about 10 roentgens per hour the totalradiation dosage being in the range of 0.001 to 3 megaroentgens of gammarays and about 3 10 to 10 fast neutrons per cm. sufficient tosignificantly alter the normal parafiEin content of said wax.

2. A process which comprises subjecting petroleum wax having a meltingpoint in the range of to F. to high intensity ionizing radiationconsisting essentially of mixed gamma-neutron radiation from a nuclearreactor for a time sufficient to significantly alter the nor malparafiin content of said wax, the total radiation dosage being in therange of 0.001 to 3 megaroentgens of gamma rays and in the range of 3X10to 15 fast neutrons per cmP.

References Cited in the file of this patent f UNITED STATES PATENTSMcClinton OTHER REFERENCES Apr. 24, 1956 Lawton et al.: Nature, vol.172, pages 76, 77, July Charlesby: Proc. Roy. Society" (London), vol.222A,

10 pages 6074, Feb. 23, 1954.

1. A PROCESS FOR TREATING REFINED PETROLEUM WAX WHICH COMPRISESSUBJECTING SAID WAX TO IONIZING RADIATION COMPRISING FAST NEUTRONS OFINTENSITY OF AT LEAST ABOUT 108 NEUTRONS PER CM.2 PER SECOND AND GAMMARAYS OF INTENSITY OF AT LEAST ABOUT 104 ROENTGENS PER HOUS THE TOTALRADIATIONS DOSAGE BEING IN THE RANGE OF 0.001 TO 3 MEGAROENTGENS OFGAMMA RAYS AND ABOUT 3X1011 TO 1015 FAST NEUTRONS PER CM.2 SUFFICIENT TOSIGNIFICANTLY ALTER THE NORMAL PARAFFIN CONTENT OF SAID WAX.